In addition to stimulating visual responses, light induces a range of circadian, neuroendocrine and neurobehavioral non-visual responses in humans. These effects are mediated primarily via a novel non-rod, non-cone photoreceptor, which is most sensitive to blue light (lambda_max 480nm) and exhibits different sensitivity to the spectrum, timing, intensity, duration and pattern of exposure as compared to visual responses. The discovery of this novel photoreceptor has led to consideration of the nonvisual effects of light as an important element of healthy lighting design in addition to vision. Before application of these new findings, however, it is necessary to first understand, and then model how the nonvisual system responds to light. One challenging aspect is the fact that the nonvisual system adapts its responses to changes in light intensity and spectral composition over a much longer timeframe than the visual system. Here, we propose a functional model of the nonvisual light-response relationship that combines temporal integration and a static nonlinear function.